The human fibroblast and human immune interferon genes and their expression in homologous and heterologous cells

Expression of Toll-like receptors in verruca and molluscum contagiosum

Recent studies indicate that several Toll-like receptors (TLRs) are implicated in recognizing viral structures and instigating immune responses against viral infections. The aim of this study is to examine the expression of TLRs and proinflammatory cytokines in viral skin diseases such as verruca vulgaris (VV) and molluscum contagiosum (MC). Reverse transcription-polymerase chain reaction and immunostaining of skin samples were performed to determine the expression of specific antiviral and proinflammatory cytokines as well as 5 TLRs (TLR2, 3, 4, 7, and 9). In normal human skin, TLR2, 4, and 7 mRNA was constitutively expressed, whereas little TLR3 and 9 mRNA was detected. Compared to normal skin (NS), TLR3 and 9 mRNA was clearly expressed in VV and MC specimens. Likewise, immunohistochemistry indicated that keratinocytes in NS constitutively expressed TLR2, 4, and 7; however, TLR3 was rarely detected and TLR9 was only weakly expressed, whereas 5 TLRs were all strongly expressed on the epidermal keratinocytes of VV and MC lesions. In addition, the mRNA expression of IFN-beta and TNF-alpha was upregulated in the VV and MC samples. Immunohistochemistry indicated that IFN-beta and TNF-alpha were predominantly localized in the granular layer in the VV lesions and adjacent to the MC bodies. Our results indicated that VV and MC skin lesions expressed TLR3 and 9 in addition to IFN-beta and TNF-alpha. These viral-induced proinflammatory cytokines may play a pivotal role in cutaneous innate immune responses.

Quantitative multiplex real-time PCR for the sensitive detection of interferon beta gene induction and viral suppression of interferon beta expression

Interferon-beta (IFN-beta) protein and activity can be detected by enzyme immunoassays and biological assays. However, precise quantification of low IFN-beta mRNA concentrations, which is advantageous for investigating IFN-beta gene expression in small tissue samples or during the early stage of a virus infection, remains a challenge. Therefore, we established a quantitative real-time PCR (qPCR) for IFN-beta and the housekeeping gene porphobilinogen deanimase (PBGD) in separated assays as well as in a multiplex procedure. Sensitivity for both the templates was less than 20 copies with an intra- and interassay variability of less than 5%. IFN-beta qPCR was utilized to optimize IFN-beta induction with dsRNA polyinosic-polycytidylic acid (poly I:C), delivered by a liposomal transfection agent for reproducible but low, non-cell-toxic IFN-beta concentrations. For studying coxsackievirus B3 (CVB3) interference with IFN-beta expression, CVB3 infected fibroblasts were induced with poly I:C. A significant reduction of IFN-beta mRNA but not PBGD mRNA was demonstrated 5 h after CVB3 infection, indicating a specific inhibition of IFN-beta expression by CVB3 on the mRNA level, in addition to previously reported effects on the translation/post-translation level. In conclusion, sensitive IFN-beta/PBGD multiplex qPCR proved to be a useful tool to study viral interaction with IFN-beta expression.

Highly sensitive detection of gene expression of an intronless gene: amplification of mRNA, but not genomic DNA by nucleic acid sequence based amplification (NASBA)

NASBA is an isothermal nucleic acid amplification reaction that amplifies mRNA in a dsDNA background. Although similar to the sensitive reverse transcription/polymerase chain reaction (RT-PCR) in mRNA detection, NASBA is not prone to give false positive results caused by genomic dsDNA. Therefore, NASBA is unique for sensitive detection of transcription of intronless genes, which preclude strategies such as intron spanning primer pairs to control false positive results in RT-PCR. Using NASBA, mRNA of the intronless human interferon-beta gene was demonstrated with a sensitivity of 10 copies, whereas 100 ng genomic DNA gave a negative result.

Two monokines, interleukin 1 and tumor necrosis factor, render cultured vascular endothelial cells susceptible to lysis by antibodies circulating during Kawasaki syndrome

Kawasaki syndrome (KS) is an acute febrile illness of early childhood characterized by diffuse vasculitis and marked immune activation. The present study was undertaken to determine whether the acute phase of KS is associated with circulating cytotoxic antibodies directed to target antigens induced on vascular endothelium by the monokines, IL-1, or tumor necrosis factor (TNF). Sera from 20 patients with acute KS, 11 patients in the convalescent phase of KS, and 17 age-matched controls were assessed for complement-dependent cytotoxic activity against 111In-labeled human endothelial cells (HEC), dermal fibroblasts, and vascular smooth muscle cells. Sera from patients with acute KS but not the other subject groups caused significant (p less than 0.01) complement-mediated killing of IL-1- or TNF-stimulated HEC. None of the sera tested had cytotoxicity against control HEC cultures or the other target cell types, with or without IL-1 or TNF pretreatment. Expression of the IL-1- or TNF-inducible target antigens on endothelial cells was rapid and transient, peaking at 4 h and disappearing after 24 h despite continued incubation with monokine. In contrast, we have previously shown that IFN-gamma requires 72 h to render HEC susceptible to lysis with acute KS sera. Serum adsorption studies demonstrated that IL-1- and TNF-inducible endothelial target antigens are distinct from IFN-gamma-inducible antigens. These observations suggest that mediator secretion by activated monocyte/macrophages could be a predisposing factor to the development of vascular injury in acute KS. Although our present observations have been restricted to KS, the development of cytotoxic antibodies directed to monokine-inducible endothelial cell antigens may also be found in other vasculitides accompanied by immune activation.

Oncostatin M: a growth regulator produced by differentiated histiocytic lymphoma cells

A polypeptide termed oncostatin M, which inhibits the replication of A375 melanoma and other human tumor cells, but not normal human fibroblasts, has been isolated from serum-free supernatants of U-937 histiocytic lymphoma cells that have been induced to differentiate into macrophage-like cells following treatment with the phorbol ester phorbol 12-myristate 13-acetate. No such growth inhibitory activity is detected in the supernatant of untreated U-937 cells, indicating that the protein is induced or increased in expression in the phorbol ester-induced differentiated cells. Oncostatin M is stable between pH 2 and 11 and after heating for 1 hr at 56 degrees C but is not stable at 90 degrees C. Purification of oncostatin M has been achieved by gel chromatography and reversed-phase HPLC, using sequentially acetonitrile and n-propanol in the presence of aqueous trifluoroacetic acid. The apparent molecular weight of oncostatin M is approximately 18,000, as determined by gel chromatography, and 28,000, as determined by polyacrylamide gel electrophoresis. The amino-terminal amino acid sequence of the purified polypeptide has been determined. No substantial sequence homology between oncostatin M and other proteins was found, including other tumor cell inhibitory proteins produced by mononuclear cells. Oncostatin M, therefore, appears to represent a distinct cell growth regulator.

Natural killer cell response to interferons

The availability of recombinant interferons has facilitated a comparison of the in vitro effects of interferon-alpha and -gamma upon human natural killer (NK) cells. In the absence of interferon high and low NK responders exist. Repeated testing of the same individuals revealed different but stable NK patterns to in vitro addition of interferon-alpha and -gamma Furthermore, the NK cell response patterns differed depending on whether the interferons were administered in combination or separately. These studies suggest new complexities that must be addressed in the planning and execution of clinical interferon trials. The pattern of responsiveness of human NK cells to interferon-alpha or -gamma or both is highly variable, but stable, within a given individual.

Recombinant human tumor necrosis factor increases mRNA levels and surface expression of HLA-A,B antigens in vascular endothelial cells and dermal fibroblasts in vitro

Recombinant human tumor necrosis factor (TNF), purified to greater than 99% homogeneity, increases surface expression of class I major histocompatibility complex (MHC) antigens to a maximum of 9-fold on cultured human endothelial cells (HEC) and human dermal fibroblasts (HDF). The increase is concentration dependent (peak 20-100 units/ml) and time dependent (nearly maximal by 4 days); expression remains elevated in the continued presence of TNF and requires greater than 7 days to return to basal levels upon TNF withdrawal. The increase in surface expression appears to result from increases in steady-state mRNA levels for the class I antigens, although the increase in mRNA is proportionately greater than for surface expression. No surface expression of or mRNA for class II MHC antigens is detectable in either control or TNF-treated HEC or HDF. These effects are similar to those produced by leukocyte or fibroblast (type I) interferons (IFNs). The protein synthesis inhibitor cycloheximide (CHX), when added coincidentally with type I IFNs, leads to superinduction of mRNA for class I MHC antigens and, unexpectedly, leads to the appearance of mRNA for class II MHC antigens. CHX has no effect by itself upon mRNA levels for class I or class II MHC antigens, nor does it modulate the increases in mRNA produced by immune (type II) IFN. Most interesting, CHX blocks the increase in mRNA for class I MHC antigens induced by TNF. Thus TNF appears to act on MHC gene expression through a newly synthesized protein intermediate. Our results provide direct evidence that TNF can modulate gene expression in normal (untransformed) cell types and contribute to understanding the complex nature of MHC gene regulation. Finally, they suggest that TNF may act in vivo as an immunoregulatory molecule.

Internal duplication in human alpha 1 and beta 1 interferons

Metric analysis of the nucleotide sequence of the intron-free human interferon beta 1 (IFN-beta 1) gene by using the Sellers TT algorithm revealed that this gene contains two major repeated segments, which span the entire coding region. These repeats are each approximately 300 nucleotides in length and have 45% identical aligned nucleotides (common bases). When these metrically aligned DNA repeats were translated into amino acids, 9 (19%) of the 47 in-phase amino acid residues were identical (common acids). This internal duplication was also apparent on visual inspection of the amino acid sequence of IFN-beta 1. In addition, metric analysis of the nucleotide sequence of the intron-free IFN-alpha 1 gene showed that this gene also contains two repeats, each approximately 300 nucleotides long, having 47% common bases and 19% common acids. Since the IFN-alpha 1 and -beta 1 genes are known to be related (by the present metric analysis they contain 53% common bases and 45% common acids), a consensus DNA sequence was derived from all four of these repeats. Manual alignment of the separate metric alignments corresponding to the two halves of the IFN-alpha 1 and -beta 1 genes provided a composite alignment with 58% of the alignment positions having the same nucleotide in at least three of the four repeats. When this composite nucleotide alignment was translated to define a composite alignment of the four protein segments, 10 (31%) of the 32 in-phase amino acid residues contained the same amino acid in at least three of the four segments. These sequences relationships provide insight into the origin of the IFN-alpha 1 and -beta 1 genes and furnish an additional basis for comparing them with other related genes.

Inhibition of human cytomegalovirus replication by 9-(1,3-dihydroxy-2-propoxymethyl)guanine alone and in combination with human interferons

The inhibitory action of 9-(1,3-dihydroxy-2-propoxymethyl)guanine on the replication of human cytomegalovirus was studied. Three laboratory strains (AD-169, Towne, and Davis) and three early passage (less than 10) clinical isolates were all inhibited in yield inhibition assays. In cultures infected with AD-169, virus yields could be inhibited if the drug was added as late as 3 days after the replication cycle had begun. The effects of the drug were fully reversible during the first 4 days of the viral replication cycle. Viral infectivity and viral DNA synthesis were reduced more than viral protein synthesis. Synergistic antiviral effects were observed with beta-cysteine, and to a lesser extent, with beta-serine recombinant interferons, but only over a narrow range of dose combinations.

Comparison of antiviral activities of cloned and native human interferons against herpes simplex virus types 1 and 2 and human cytomegalovirus

Five recombinant alpha interferons and two recombinant beta interferons have been tested for their ability to inhibit yields of herpes simplex virus types 1 and 2 and human cytomegalovirus in human embryonic lung cells. All of the alpha species and both of the beta forms (cysteine and serine) were active against the herpesviruses tested in this study. Neither the recombinant alpha nor the recombinant beta interferons exceeded the activity of the native species against herpes simplex viruses types 1 and 2. However, the recombinant beta interferons inhibited cytomegalovirus more than either the native beta or the alpha interferon species with the exception of interferon alpha K (alpha 6).

Isolation of novel human genomic DNA clones related to human interferon-beta 1 cDNA

Southern blot-hybridization analyses of human DNA (from Namalwa lymphoblastoid cells) digested with the restriction endonuclease EcoRI were carried out under optimal conditions with two human fibroblast interferon (IFN-beta 1) cDNA probes, pD19 and pD24, which contain IFN-beta 1 inserts 0.8 and 0.7 kilobase (kb) long, respectively. The analyses revealed the presence of several hybridizable DNA fragments, including two of lengths 6.8 and 5.5 kb, in addition to the classical IFN-beta 1 genomic DNA fragment of length approximately equal to 2.0 kb. We have screened a human DNA library in lambda bacteriophage Charon 4A by using a 32P-labeled IFN-beta 1 insert cDNA (pD24) and thereby isolated six strongly positive human genomic DNA clones. One of these (lambda B37) represents the classical human IFN-beta 1 gene; another (lambda B37) contains a 6.8-kb EcoRI DNA fragment(s) which cross-hybridizes with the IFN-beta 1 cDNA insert probes pD19 and pD24; and the remaining four (which are identical to each other and are exemplified by lambda B4) contain two EcoRI DNA fragments approximately 5.5 and 9 kb long which also cross-hybridize the IFN-beta 1 cDNA probes. A mRNA 0.9 kb long derived from the classical IFN-beta1 gene is expressed in poly(I) . poly(C)-induced human diploid fibroblasts (FS-4 strain). Induced FS-4 cells also contain polyadenylylated RNA 1.8, 3, 5, and approximately equal to 8 kb long derived from the lambda B3 gene, all of which appear to code for biologically active human IFN-beta as tested by using the Xenopus laevis oocyte translation assay. These data strongly indicate that lambda B3 represents a novel functional IFN-beta gene. A 12-kb polyadenylylated RNA, derived from lambda B4, is expressed constitutively at a low level in FS-4 cells, but the amount of this RNA increases 5-7 hr after exposure of the cells to poly(I) . poly(C).

Human fibroblast interferon RNA transcripts of different sizes in poly(I).poly(C) induced cells

Northern blot analysis reveals that total RNA from human fibroblastoid cells (MG 63) induced with poly(I).poly(C) under conditions of IFN-beta production, contains predominantly a +/- 1,200 nucleotide long poly (A) mRNA (mRNA.M) which hybridizes with a Hu IFN-beta cDNA specific probe. But hybridization with this probe also enabled the detection of a polyadenylated RNA (RNA.I) with a length of between 3.5 kb-3.8 kb, representing 0.6% of the total hybridizable cellular RNA in superinduced cells. Mapping shows that the RNA.I contains all the sequence information present in mRNA.M. Furthermore, it also hybridizes to sequences, located downstream from the IFN-beta gene up to 2.5 kb beyond its poly A attachment site, while no hybridization to fragments located upstream of the IFN-beta mRNA cap site was observable. Hence this RNA.I corresponds to a transcript that starts at the same position as the major mRNA.M but which extends up to 2.5 kb beyond the 3'-end of mRNA.M where another polyadenylation signal is located.

Improved plasmid vectors with a thermoinducible expression and temperature-regulated runaway replication

Improved expression vectors have been constructed which are derived from runaway-replication mutants of plasmid R1 and carry the strong leftward promoter (pL) of bacteriophage lambda. The activity of this promoter is controlled by a temperature-sensitive repressor, product of the phage gene cI cloned on a compatible plasmid. Heat induction leads to amplification of the plasmid copy number and at the same time turns on the promoter. At a short distance downstream from the promoter, unique EcoRI, BamHI, XbaI and HindIII sites are present. This system was used for high level expression of the T4 DNA-ligase gene; 3 h after induction the ligase amounted to about 20% of total cellular protein.

Deletion mapping of the inducible promoter of human IFN-beta gene

Human fibroblast cells produce beta-type interferon only in response to viral infection or treatment with an inducer such as poly(rI) X poly(rC); this event is most probably controlled at the transcriptional level (for review see ref. 1). To study the induction process, we inserted the human fibroblast interferon (IFN-beta) gene, with or without its promoter region, into recombinant simian virus 40 (SV40) plasmid vectors which subsequently were transfected into monkey AP-8 cells. We report here that upon induction with poly(rI) X poly(rC) there was a 10-30-fold increase in IFN-beta synthesis. This inducer had no effect on interferon production when the coding region only was inserted into the vector plasmid, which indicates that the promoter region is required for inducibility of this gene. Deletion mapping implicates the region between nucleotides -144 and -186 from the mRNA initiation site in the specific regulation of the IFN-beta gene. This region contains a sequence that is remarkably homologous with a consensus sequence found in the 5' flanking region of steroid hormone responsive genes, which might be involved in binding the progesterone-receptor complex.